Thermal management systems are used to cool components, such as turbine blades, in aircraft propulsion engines. For aircraft operating at Mach 3 or less these systems employ bleed air from the engine as the heat sink. As the aircraft exceeds Mach 3, the air stagnation temperature, in the engine, rises rapidly rendering the bleed air ineffective as a heat sink. An obvious alternate heat sink is the engine's fuel. However, the relatively low thermal stability temperature of conventional jet engine fuels limits their heat sink capability to temperatures at which they begin to coke. This coking temperature is about 450.degree. K. (350.degree. F.) for Jet Propellant(JP)-4 and about 650.degree. K. (700.degree. F.) for JP-7. In aircraft operating at speeds greater than Mach 3the temperature of the engine's components can easily exceed these limits. In such cases the fuel cannot be used directly for cooling but instead must be used to cool bleed air or some other stable fluid in an intermediate cooling loop. The intermediate cooling loop requires, for safety reasons, buffered heat exchangers which have a buffer space between the fuel and the bleed air which needs to be monitored for leaks of either fuel or oxidant.
Endothermic fuels are fluids which with the addition of heat and in the presence of a catalyst decompose into two, or more, gaseous compounds at least one of which is combustible. Because of their sensible and latent heat capacities and their endothermic chemical reaction energy absorbtion mechanism,endothermic fuels have higher heat sink capabilities than Jet Propellants.
Accordingly, for aircraft operating at speeds greater than Mach 3there is a need for an engine thermal management system that uses an endothermic fluid as a heat sink and as fuel for the engine.